In a conventional process for producing a labeled, synthetic resin molded article by integral molding (in-mold labeling), printing is first conducted on a base consisting of a stretched or unstretched extruded film of crystalline polypropylene, a cast film of crystalline polypropylene, a synthetic paper, a metal foil, or the like. Subsequently, the printed base is laminated on its back side with a film of a low-melting resin, such as a low-density polyethylene, an ethylene-vinyl acetate copolymer, or the like, by direct extrusion laminating, or the printed base is coated on the back side with a solvent-based adhesive prepared by dissolving a low-melting resin, such as poly(vinyl acetate), an ethylene-vinyl acetate copolymer, or the like, in a solvent or with a latex-type adhesive (liquid resinous adhesive of a heat-sensitive type) by means of a gravure coater or the like and the coating is then dried, thereby to produce a label of a laminated structure. This label is then placed beforehand on an inner wall of a mold, and a molding resin such as polypropylene, polyethylene, or other resin is fed directly to the cavity of the mold and shaped by means of injection molding, blow molding, in-mold bead-foaming molding, or the like (European Patents 254,923 and 281,701, U.S. Pat. Nos. 4,837,075 and 4,986,866, and JP-A-58-69015). (The term "JP-A" as used herein means an "unexamined published Japanese patent application".)
Also in the case of applying a laminated-structure label of the above kind to the surface of a cup-type molded article obtained by shaping a polypropylene or polyethylene resin sheet, substantially the same procedure has been employed, that is, the label is inserted into a mold and the resin sheet in a heated state is then shaped into a cup in the mold by means of differential pressure forming utilizing a pressure difference (vacuum forming or pressure forming).
On the other hand, in retail stores and the like as the final stage of distribution, labeling for displaying a bar code, a dealer name, or other information on contents-filled containers to be sold as goods is being practically conducted by placing a laminated-structure label printed with a bar code, a dealer name, or other information on the surface of such a container or a package therefor, e.g., bag, and then pressing the label with a heated iron or the like to heat-bond the label to the container or package.
The label base, which usually is a synthetic paper or a converted paper prepared by coating a film with a pigment, has undergone a surface-smoothing treatment such as calendering or stretching so as to attain good finish of prints to be obtained therefrom. An in-mold label is prepared by laminating a hot melt resin adhesive film having a low-melting point directly to the base, and then embossing the thus-formed hot melt resin adhesive layer with an embossing roll in order to easily feed the label to a cavity of a mold by means of an insertor and to prevent the occurrence of blistering on labeled molded articles (U.S. Pat. No. 4,986,866). Man can hit a use of an organic solvent-based adhesive in place of hot melt resin adhesive. It is coated on the base and dried to form an adhesive layer, and then the adhesive layer is embossed to bear a gravure pattern on its surface.
Although it has been attempted to form such a liquid-based adhesive layer by coating a water-based resinous adhesive such as, for example, an aqueous latex or emulsion to the base in place of the hot melt resin adhesive, it has been impossible to form an embossed or gravure pattern or a similar pattern on the surface of the adhesive layer.
Because of the above, in-mold labels having an adhesive layer formed by coating such a water-based adhesive have had a problem that containers to which such labels can be applied are limited in shape, because such in-mold labels are more apt to develop blisters when used in in-mold application as compared with the label having an adhesive layer with an embossed surface and the label having an adhesive layer formed from an organic solvent-based adhesive and bearing a gravure pattern.